Need urgent help calculating a concentration!!!

[Leni]

Hi,
i'm facing a very interesting problem and i'd like to hear more oppinions. So, i got a work method wich says the following at the chapter "Standard preparation":
Quote: "Dilute 4ml of 1.25mg/l solution of 'x'(compound is not so important) standard solution in acetonitril to 25ml with diluent.(200ppm)"

So basically it says if i understand correctly, that by diluting 4ml to 25ml, of this 1,25mg/l solution(this solution comes as standard)...i obtain a conc. of 200ppm. According to my calculations the concentration obtained is 0.2ppm
Here's how i calculated:

1,25[mg/l] x 4[ml] / 25[ml] = 0.2[mg/l] = 0.2ppm

Please give me some advice! thank you

[Peter Apps]

Your calculation looks good to me. When discussing this in class you can also point out that "ppm" is a vague term which can mean different things according to how it is expressed - mole/mole, mass/mass, mass/vol etc

Peter

[Leni]

Your calculation looks good to me. When discussing this in class you can also point out that "ppm" is a vague term which can mean different things according to how it is expressed - mole/mole, mass/mass, mass/vol etc

Peter

Thanks for your reply... i guess in this case it's ppm that stands for mass/volume...no matter how i looked at it, it just didn't add up to 200ppm

[Peter Apps]

Your calculation looks good to me. When discussing this in class you can also point out that "ppm" is a vague term which can mean different things according to how it is expressed - mole/mole, mass/mass, mass/vol etc

Peter

Thanks for your reply... i guess in this case it's ppm that stands for mass/volume...no matter how i looked at it, it just didn't add up to 200ppm

It is probably supposed to be 200 ppb - doubtless a typo and poor proof reading.

Peter

[Andy F]

Your calculation looks good to me. When discussing this in class you can also point out that "ppm" is a vague term which can mean different things according to how it is expressed - mole/mole, mass/mass, mass/vol etc

Peter

Thanks for your reply... i guess in this case it's ppm that stands for mass/volume...no matter how i looked at it, it just didn't add up to 200ppm

It is probably supposed to be 200 ppb - doubtless a typo and poor proof reading.

Peter

Could also be that the standard is 1.25 mg/ml which would make the 200 mg/l correct, still a typo though.

[Leni]

Thanks very much guys...yes, it must be some typo error for sure...now we are trying to find out where the error occured...of course everyone is just like "hm...donno...don't remember" ...very funny situation this.

[Pepter]

Hi,
i'm facing a very interesting problem and i'd like to hear more oppinions. So, i got a work method wich says the following at the chapter "Standard preparation":
Quote: "Dilute 4ml of 1.25mg/l solution of 'x'(compound is not so important) standard solution in acetonitril to 25ml with diluent.(200ppm)"

So basically it says if i understand correctly, that by diluting 4ml to 25ml, of this 1,25mg/l solution(this solution comes as standard)...i obtain a conc. of 200ppm. According to my calculations the concentration obtained is 0.2ppm
Here's how i calculated:

1,25[mg/l] x 4[ml] / 25[ml] = 0.2[mg/l] = 0.2ppm

Please give me some advice! thank you

200ppb not ppm (type error)

[Leni]

Hi,
i'm facing a very interesting problem and i'd like to hear more oppinions. So, i got a work method wich says the following at the chapter "Standard preparation":
Quote: "Dilute 4ml of 1.25mg/l solution of 'x'(compound is not so important) standard solution in acetonitril to 25ml with diluent.(200ppm)"

So basically it says if i understand correctly, that by diluting 4ml to 25ml, of this 1,25mg/l solution(this solution comes as standard)...i obtain a conc. of 200ppm. According to my calculations the concentration obtained is 0.2ppm
Here's how i calculated:

1,25[mg/l] x 4[ml] / 25[ml] = 0.2[mg/l] = 0.2ppm

Please give me some advice! thank you

200ppb not ppm (type error)

Thanks for your kind reply...greatly appreciated